High order exactly divergence-free Hybrid Discontinuous Galerkin Methods for unsteady incompressible flows

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• 作者：Christoph Lehrenfeld^a ; ^{christoph.lehrenfeld@uni-muenster.de" class="auth_mail" title="E-mail the corresponding author} ; Joachim Schö ; berl^b ; ^{joachim.schoeberl@tu-wien.ac.at" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Navier&ndash ; Stokes equations ; Hybrid Discontinuous Galerkin Methods ; H(div)-conforming finite elements ; Exactly divergence-free ; Operator-splitting ; Reduced stabilization
• 刊名：Computer Methods in Applied Mechanics and Engineering
• 出版年：2016
• 出版时间：1 August 2016
• 年：2016
• 卷：307
• 期：Complete
• 页码：339-361
• 全文大小：865 K

文摘

In this paper we present an efficient discretization method for the solution of the unsteady incompressible Navier–Stokes equations based on a high order (Hybrid) Discontinuous Galerkin formulation. The crucial component for the efficiency of the discretization method is the distinction between stiff linear parts and less stiff non-linear parts with respect to their temporal and spatial treatment.

Exploiting the flexibility of operator-splitting time integration schemes we combine two spatial discretizations which are tailored for two simpler sub-problems: a corresponding hyperbolic transport problem and an unsteady Stokes problem.

For the hyperbolic transport problem a spatial discretization with an Upwind Discontinuous Galerkin method and an explicit treatment in the time integration scheme is rather natural and allows for an efficient implementation. The treatment of the Stokes part involves the solution of linear systems. In this case a discretization with Hybrid Discontinuous Galerkin methods is better suited. We consider such a discretization for the Stokes part with two important features: a35af16eb38e9f4d1ba362d93f97f" title="Click to view the MathML source">H(div)$H\left(\text{div}\right)$-conforming finite elements to guarantee exactly divergence-free velocity solutions and a projection operator which reduces the number of globally coupled unknowns. We present the method, discuss implementational aspects and demonstrate the performance on two and three dimensional benchmark problems.